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. 2022 Dec;11(1):507-518.
doi: 10.1080/22221751.2022.2031310.

Identification of methicillin-resistant Staphylococcus aureus ST8 isolates in China with potential high virulence

Xinyi Wang  1 , Huilin Zhao  1 , Bingjie Wang  1 , Ying Zhou  1 , Yanlei Xu  2 , Lulin Rao  3 , Wenxiu Ai  3 , Yinjuan Guo  1 , Xiaocui Wu  1 , Jingyi Yu  1 , Longhua Hu  4 , Lizhong Han  5 , Shuying Chen  3 , Liang Chen  6   7 , Fangyou Yu  1
Affiliations

Identification of methicillin-resistant Staphylococcus aureus ST8 isolates in China with potential high virulence

Xinyi Wang et al. Emerg Microbes Infect. 2022 Dec.

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) ST8 strains have spread worldwide, causing outbreaks in various regions. However, this clone has only been sporadically reported in China. Consequently, detailed information regarding the phylogeny and potential virulence of S. aureus ST8 strains in China remains unknown. In this study, we characterized six ST8 strains collected from three tertiary hospitals in China, including three MRSA (MR50, MR526, and MR254) and three MSSA (H78, H849 and H863). Whole genome sequencing and phylogenetic analysis showed that the six strains formed two separate clusters, including two (MR50 and MR526) and four (MR254, H78, H849 and H863) isolates, respectively. Among them, MR50 and MR526 harboured spa t008, SCCmec IVa, arginine catabolic mobile element, and were phylogenetically close to the epidemic USA300 strains, while other four strains belonged to spa t9101 and formed a unique branch. MR254 carried a novel hybrid SCCmec element (namely SCCmec254). Same as the USA300 prototype strain LAC, the China S. aureus ST8 strains produced weak biofilms except MR254. Among them, MR254 had significantly stronger haemolysis ability and higher α-toxin levels than others, while MR526 showed comparable haemolysis and α-toxin production levels as USA300-LAC. In mouse skin abscess model, MR254 showed particularly strong invasions, accompanied by necrosis, while MR526 exhibited similar infection levels as USA300-LAC. These data suggested that the China MRSA ST8 isolates (e.g. MR254 and MR526) were highly virulent, displaying higher or similar virulence potential as the epidemic USA300 strain. Active surveillance should be enacted to closely monitor the further spread of these hyper-virulent MRSA strains in China.

Keywords: Methicillin-resistant Staphylococcus aureus; SCCmec cassette; ST8; pathogenicity; virulence.

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Conflict of interest statement

No potential conflict of interest was reported by the author(s).

Figures

Figure 1.
Figure 1.
Comparison of SCCmec V-254 and two available types of SCCmec.
Figure 2.
Figure 2.
Analysis for the genomes of six S. aureus ST8 isolates and USA300- FPR3757. (A) ParSNP phylogenetic tree of 1092 S. aureus genomes from RefSeq database and the present study. (B) Comparison of the genomes of MR254 and other S. aureus ST8 strains. Each circle represents one strain, MR254, H78, H849, H863, MR50, MR526 and USA300-FPR3757 from the inside out. The SCCmec cassette and phage regions are marked in the outermost ring.
Figure 3.
Figure 3.
Haemolysis ability of S. aureus ST8. (A) Haemolysis phenotype of S. aureus ST8 strains. The absorbance measured at 600 nm of each sample was converted to a percentage with A600 of the positive control value as 100%. ***p < .001, ****p < .0001. (B) The α-toxin expression of S. aureus ST8 strains quantified by ELISA. * represents p < .05.
Figure 4.
Figure 4.
Relative expressions of hla, saeR, mecA, lukF-PV and lukS-PV in S. aureus ST8 isolates. *p < .05, **p < .01, ***p < .001, ****p < .0001.
Figure 5.
Figure 5.
The PVL expression of S. aureus ST8 strains.
Figure 6.
Figure 6.
The mouse skin infections caused by S. aureus ST8. (A) Abscesses caused by S. aureus ST8. The lesion sizes of six mice in each group on the first day post-infection were shown. (B) The abscess size changes after infections pattern. (C) Pathological sections of the representative mice from each group, including two power fields (4× and 10×) of skin abscess tissues dissected.
See this image and copyright information in PMC

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